Section off the hair you want to cut and clip the rest back. Split your bangs in half using a comb. Hold one half and comb the hair down, with the comb's teeth facing out. Cut slowly below the comb, doing a little bit at a time, as if you were nipping away at the hair. Cut your bangs to your brow bone. Never try to cut them straight across; it's impossible to keep a straight line. Instead, snip at a slightly upward angle. After cutting the other half, comb your bangs down to make sure they are even.
Styling tip: Cut your hair only when it's dry. Your hair shrinks as it dries, so if you cut it when it's wet, it will end up shorter than you intended.